By October 1918 as the Great War was drawing to a close, an even greater bringer of mass death was at the height of its virulence.

Although commonly referred to as ‘Spanish flu’, we may be confident that the great flu epidemic of 1918 did not originate in Spain.

However, because Spain was neutral during the Great War, the Spanish press was free to report the illness in a way the press in other countries were not.

The fact that King Alfonso XIII, the Spanish monarch, contracted the disease and uncensored reporting created the impression that Spain was the most seriously affected country in Europe and the source of the infection.

This was not so but in the absence of adequate historical data it is impossible to identify the pandemic’s origin with absolute certainty. Instead we have competing hypotheses.

As they were well documented, the first outbreaks are widely believed to have been in March 1918 in Haskell County, Kansas, and Fort Riley, an American army base in Kansas.

Almost 20 years ago a British team of virologists identified the British base at Etaples – a major troop staging and hospital camp in France – as the centre of epidemic.

Conditions at the overcrowded camp and hospital – which treated thousands of casualties of war and chemical attacks – were ideal for the spread of a respiratory virus.

At the time the Pasteur Institute claimed that the flu originated in China, mutated in Boston, was brought to Brest by US troop ships, and spread from the battlefields of Europe to the rest of the world.

The US authorities were conscious of the impact of the epidemic on eastbound American troopships, a price President Wilson reluctantly accepted because of the imperative of rushing men to Europe.

More US service personnel succumbed to flu rather than German bullets and roughly half the flu victims died in the United States.

In 2014, Mark Humphries, a Canadian historian, suggested that the mobilisation of 96,000 Chinese labourers to work behind the British and French lines on the western front may have been the source of the pandemic.

Two years later a report in the Journal of the Chinese Medical Association found no evidence that the 1918 virus was imported to Europe via China or South-East Asia. It claimed that the virus had been circulating in Europe for months and possibly years before the 1918 pandemic.

The pandemic infected 500 million people around the world and resulted in the deaths of between 50 and 100 million people (i.e. between 3% and 5% of the world’s population a century ago).

So most people who contracted the disease survived but in some places perhaps as many as 20% did not. A 20% death rate vastly exceeds a typical flu which kills less than 1% of those infected.

The British Isles was affected by three waves of the flu epidemic. The first seems to have coincided with the arrival of US troops in the UK.

The second wave occurred between September and December 1918. A third wave occurred between February and April 1919.

The death toll from the first wave was relatively low. The second wave resulted in the highest death rates. The third wave was more lethal than the first but less so than the second.

Onset of the infection was devastatingly rapid. Those fine and healthy at breakfast could be dead by tea-time. Within hours of feeling the first symptoms of fatigue, fever and headache, some victims would rapidly develop pneumonia and start turning blue, signalling a shortage of oxygen. They would then struggle for air until they suffocated to death.

The pandemic is universally regarded as ‘the greatest medical holocaust in history’. It had at least two unusual features. First, it killed mostly young and healthy adults. Normally infants and old people are most vulnerable to flu.

Secondly, in the Northern Hemisphere the outbreak was rampant during the summer and autumn whereas flu is usually at its worst in the winter.

As Stalin observed that ‘the death of millions is a statistic; the death of one man is a tragedy’, let us look at the death of one Belfast man.

Sergeant Thomas Samuel Telford served with Machine Gun Corps (Motor) and survived the Great War.

He had served in Mesopotamia (modern Iraq) and was taken ill on his way home to be demobilised. On his arrival in the United Kingdom he was sent to a military hospital in Grantham, Lincolnshire.

There he died (officially of pneumonia but almost certainly of flu) on March 12 1919. He was only 19 when he died and is buried in Belfast City Cemetery.

Although he would have been entitled to a Commonwealth War Graves Commission headstone, he is commemorated by a rather beautiful Celtic Cross which was erected by his family.

The local historian Nigel Henderson speculates that Thomas may have sent his parents at 88 University Avenue postcards from Alexandria, Malta and Gibraltar on the way home.

It is not difficult to imagine the family’s joy at him having safely survived the war turning to grief and pain as he succumbed to great pandemic of 1918-19.

In 1918 in England and Wales around 200,000 people died. In Scotland between 27,000 and 33,000 perished and in Ireland over 18,000. These figures may well err on the low side.

The pandemic was no respecter of persons of rank and position. David Lloyd George, Georges Clemenceau and Woodrow Wilson, the three key figures at the Paris Peace conference, all contracted flu but survived. In September 1918 Lloyd George was close to death’s door. In early 1919 Woodrow Wilson’s private secretary cautioned Wilson against overwork and warned him if he did not let up he might wreck his constitution. ‘Constitution!’ exclaimed Wilson. ‘Why, man I’m already living on my by-laws!’